Image heating apparatus

Abstract

An image heating apparatus includes a cylindrical rotatable member, an exciting coil, a magnetic core, and a resin material layer provided between the exciting coil and the magnetic core. The exciting coil is a metal wire coated with heat-resistant resin. The resin material layer is provided between the exciting coil and the magnetic core and is a layer that is different from the heat-resistant resin of the metal wire. The resin material layer is provided on a surface of the magnetic core in a helical shape along the exciting coil. As viewed in a direction perpendicular to a longitudinal direction of the rotatable member, the exciting coil enters the resin material layer in a radial direction of the exciting coil.

What is claimed is: 
     
       1. An image heating apparatus for heating a toner image formed on a recording material, the image heating apparatus comprising:
 a cylindrical rotatable member including a cylindrical electroconductive layer, said rotatable member being rotatable while contacting the recording material and having a longitudinal direction; 
 an exciting coil configured to cause said electroconductive layer to generate heat through induction heating, said exciting coil being (i) a helix having a helical axis and (ii) a metal wire coated with heat-resistant resin, said exciting coil being provided in a hollow portion of said rotatable member so that the helical axis of said exciting coil is parallel to the longitudinal direction of said rotatable member; 
 a magnetic core provided inside the helix of said exciting coil and configured to induce magnetic flux generated by said exciting coil; and 
 a resin material layer provided between said exciting coil and said magnetic core, said resin material layer being a layer different from the heat-resistant resin of said metal wire, said resin material layer being provided on a surface of said magnetic core in a helical shape along said exciting coil, 
 wherein, in a plane parallel to the longitudinal direction of said rotatable member and cutting said magnetic core and said exciting coil, said resin material layer includes a recessed portion, and said exciting coil enters the recessed portion of said resin material layer in a radial direction of said magnetic core as viewed in a direction perpendicular to the longitudinal direction of said rotatable member. 
 
     
     
       2. The image heating apparatus according to  claim 1 , wherein, in a region other than a region where said exciting coil is wound around said magnetic core, said resin material layer is absent on a surface of said magnetic core and said magnetic core is exposed. 
     
     
       3. The image heating apparatus according to  claim 1 , wherein, said resin material layer is polyphenylene sulfide resin. 
     
     
       4. The image heating apparatus according to  claim 1 , wherein said magnetic core has a non-endless shape and magnetic flux coming out of opposite ends of said magnetic core passes through an outside of said electroconductive layer. 
     
     
       5. The image heating apparatus according to  claim 4 , wherein ninety percent or more of the magnetic flux passing through an inside of the magnetic core passes through the outside of said electroconductive layer. 
     
     
       6. The image heating apparatus according to  claim 1 , wherein said exciting coil is formed by a plurality of said metal wires, and
 wherein said resin material layer includes a plurality of the recessed portions corresponding to the plurality of said metal wires, respectively. 
 
     
     
       7. The image heating apparatus according to  claim 1 , wherein said exciting coil is formed by a plurality of said metal wires, and
 wherein respective distances between the plurality of said metal wires and said magnetic core are substantially the same. 
 
     
     
       8. An image heating apparatus for heating a toner image formed on a recording material, the image heating apparatus comprising:
 a cylindrical rotatable member including a cylindrical electroconductive layer, said rotatable member being rotatable while contacting the recording material and having a longitudinal direction; 
 an exciting coil configured to cause said electroconductive layer to generate heat through induction heating, said exciting coil being (i) a helix having a helical axis and (ii) a metal wire coated with heat-resistant resin, said exciting coil being provided in a hollow portion of said rotatable member so that the helical axis of said exciting coil is parallel to the longitudinal direction of said rotatable member; 
 a magnetic core provided inside the helix of said exciting coil and configured to induce magnetic flux generated by said exciting coil; and 
 a resin material layer provided between said exciting coil and said magnetic core, said resin material layer being a layer different from the heat-resistant resin of said metal wire, said resin material layer being provided on a surface of said magnetic core in a helical shape along said exciting coil, 
 wherein, in a region other than a region where said exciting coil is wound around said magnetic core, said resin material layer is absent on a surface of said magnetic core and said magnetic core is exposed. 
 
     
     
       9. The image heating apparatus according to  claim 8 , wherein said resin material layer is polyphenylene sulfide resin. 
     
     
       10. The image heating apparatus according to  claim 8 , wherein said magnetic core has a non-endless shape and magnetic flux coming out of opposite ends of said magnetic core passes through an outside of said electroconductive layer. 
     
     
       11. The image heating apparatus according to  claim 10 , wherein ninety percent or more of the magnetic flux passing through an inside of the magnetic core passes through the outside of said electroconductive layer. 
     
     
       12. The image heating apparatus according to  claim 8 , wherein said exciting coil is formed by a plurality of said metal wires, and
 wherein respective distances between the plurality of said metal wires and said magnetic core are substantially the same.